Abstract Due to the competition for food, space, oxygen and due to their role as diseases vector, epibionts can negatively affect oyster farming. We assessed the efficacy of six methods commonly used for the removal of epibionts from oyster shells during farming. The experiment was conducted at an oyster farm on the Paraná coast – South Brazil. Oysters (Crassostrea gasar) were acclimated for 90 d in the cultivation system and later exposed to cleaning treatments: i) freshwater; ii) hypersaline water; iii) sodium hypochlorite solution; iv) quaternary ammonia solution; v) exposure to air; vi) hydroblasting; and vii) no cleaning procedure (control). After treatment, oysters were kept in the cultivation system for 15 and 30 d – when the total incrustation and mortality were measured. Epibionts from nine phyla were identified. The most abundant were Arthropoda (Crustacea) (62.5%), Mollusca (33.8%) and Annelida (3.1%). Freshwater [15 (n = 2263 epibionts) and 30 days (n = 2822 epibionts)] and hydroblasting [15 (n = 1850 epibionts) and 30 days (n = 2389 epibionts)] treatments were the most efficient to reduce epibionts and caused lower rates of oyster mortality [15 (5.0 and 3.33%, respectively) and 30 days (1.67 and 6.67%, respectively)].

ABSTRACT This study aimed to evaluate the apparent digestibility coefficients (ADCs) of dry matter, crude protein, gross energy, and minerals of marine fish meal (MFM), salmon meal (SM), tilapia by-product meal (TBM), meat and bone meal (MBM), poultry by-product meal (PBM), blood meal (BM), and feather meal (FM) by silver catfish Rhamdia voulezi. Groups of 12 fish were fed the experimental diet three times a day until apparent satiation, and the fecal samples were collected from an accumulation device. SM and PBM exhibited the highest digestibility values for dry matter, crude protein, and gross energy, while MBM and FM presented significantly lower ADCs for dry matter. BM and FM exhibited higher ADCs for phosphorus, 65.05 and 63.87%, respectively. The ADCs for calcium were 58.8% for MFM, 56.69% for TBM, and 60.08% for PBM. PBM and FM had the highest iron ADCs, 44.01 and 46.29%, respectively. Magnesium ADCs ranged from 44.87% for MBM to 75.50% for TBM. BM had the highest digestibility for zinc (62.77%), whereas MBM (36.68%) and FM (39.39%) had the lowest. In general, SM and PBM showed higher values as feedstuffs for silver catfish feeds. At the same time, the digestibility was lower for TBM and MBM for macronutrients and minerals such as phosphorus, iron, and zinc.

Abstract In this work, we identified the bacterial microbiota associated with farmed oystersin estuarine regions of four states in the north eastern region of Brazil. During the drought and rainy seasons, for eight months, twenty oysters were sampled seasonally from seven different marine farms. In the laboratory, DNA extraction, amplification, and sequencing of the 16S rRNA gene were performed to establish the taxonomic units. We identified 106 genera of bacteria belonging to 103 families, 70 orders, 39 classes, and 21 phyla. Out of the total, 40 of the genera represented bacteria potentially pathogenic to humans; of these, nine are known to cause foodborne diseases and six are potentially pathogenic to oysters. The most prevalent genera were Mycoplasma, Propionigenium, Psychrilyobacter, and Arcobacter. The results indicate the need for more systematic monitoring of bacteria of the genus Mycoplasma in oyster farming operations in the Brazilian north eastern region. Currently, Mycoplasma is not one of the microorganisms analysed and monitored by order of Brazilian legislation during the oyster production and/or commercialization process, even though this genus was the most prevalent at all sampling points and presents pathogenic potential both for oysters and for consumers.